Hydraulic control device for automatic transmission

Abstract

A hydraulic control device for an automatic transmission capable of preventing engine racing and tie-up by controlling disengagement side oil pressure in accordance with an input torque and an oil temperature. Gear-change execution controller U 4 controls drain timings T 1 and T 3 and a drain gradient δP of the disengagement side oil pressure acting on the frictional engagement elements of the disengagement side according to the magnitude of the input torque and elevation of the oil temperature in torque phase control wherein both the engagement side oil pressure and the disengagement side oil pressure are controlled.

What is claimed is:  
     
       1. A hydraulic control device for an automatic transmission provided with an input shaft which receives torque from an output shaft of an engine, an output shaft for outputting torque to the wheels, a plurality of frictional engagement elements for changing a torque transfer path between the input and output shafts, and hydraulic servos for engaging or disengaging the frictional engagement elements, wherein an up-shift to a predetermined gear ratio is achieved by engaging first frictional engagement elements at a predetermined engagement side oil pressure and disengaging second frictional engagement elements at a predetermined disengagement side oil pressure, said hydraulic control device comprising: 
       input torque calculation means for calculating input torque; and  
       gear-change execution control means for controlling the drain timing of the disengagement side oil pressure, acting on the second frictional engagement elements, in accordance with the calculated input torque in a torque phase control wherein both the engagement side oil pressure and the disengagement side oil pressure are controlled, and wherein the disengagement side oil pressure is controlled by advancing the drain timing of the disengagement side oil pressure as the calculated input torque decreases.  
     
     
       2. The hydraulic control device for an automatic transmission according to  claim 1 , wherein the gear-change execution control means advances the drain timing of the disengagement side oil pressure acting on the second frictional engagement elements, in accordance with elevation of oil temperature and decrease in the calculated input torque, in the torque phase control. 
     
     
       3. The hydraulic control device for an automatic transmission according to  claim 2 , wherein the gear-change execution control means controls a drain gradient of the disengagement side oil pressure acting on the second frictional engagement elements, in accordance with the decrease in calculated input torque and with elevation of oil temperature, in the torque phase control. 
     
     
       4. The hydraulic control device for an automatic transmission according to  claim 3 , wherein the gear-change execution control means makes the drain gradient steeper as the oil temperature increases. 
     
     
       5. The hydraulic control device for an automatic transmission according to  claim 1 , wherein the gear-change execution control means controls a drain gradient of the oil pressure acting on the second frictional engagement elements, in accordance with elevation of the oil temperature and with elevation of oil temperature, in the torque phase control. 
     
     
       6. The hydraulic control device for an automatic transmission according to  claim 5 , wherein the gear-change execution control means makes the drain gradient of the oil pressure steeper as the oil temperature increases. 
     
     
       7. The hydraulic control device for an automatic transmission according to  claim 1 , wherein the gear-change execution control means controls a drain gradient of the disengagement side oil pressure acting on the second frictional engagement elements, in accordance with the calculated input torque and with elevation of oil temperature, in the torque phase control.